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Lucifuga lucayana 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Ophidiiformes Bythitidae

Scientific Name: Lucifuga lucayana Møller, Schwarzhans, Iliffe & Nielsen, 2006
Common Name(s):
English Lucayan Cave Brotula
Taxonomic Source(s): Eschmeyer, W.N. and Fricke, R. (eds). 2015. Catalog of Fishes: genera, species, references. Updated 1 October 2015. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 1 October 2015).
Taxonomic Notes: The Lucifuga genus is known as one of the most diverse stygiobiotic fishes to have been described. The taxonomy of Lucifuga species may still be incomplete due to relatively common discoveries of new species. Garcia-Machado et al. (2011) concluded that Lucifuga spp. are genetically divergent, but morphologically indistinguishable and recommends revisiting the taxonomy of the genus. Since the distribution of certain morphological characters among these species are disjointed, they possibly may not be used for classification in the future. A revision of the Lucifuga spp. of Cuba with the description of a new species is currently in preparation by Hernández et al. (Hernández, D., Casane, D., García, A., Chevalier-Monteagudo, P., Møller, P. R. and García-Machado, E.)

There are no species of Lucifuga spp. on Little Bahama Bank other than L. lucayana (Moller et al. 2006).

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(iii)+2ab(iii) ver 3.1
Year Published: 2015
Date Assessed: 2012-01-25
Assessor(s): Dooley, J., Collette, B., Aiken, K.A., Marechal, J. & Pina Amargos, F.
Reviewer(s): Cox, N.A.
Facilitator/Compiler(s): Harwell, H.
Justification:
Lucifuga lucayana has a highly patchy and restricted distribution. It has only been known to occur to a depth of 20 m in three inland cave or sink hole systems in the northern Bahamas: the Lucayan Caverns, the Zodiac Caverns, and one or two inland sink holes on Abaco Island. Its estimated area of occupancy (AOO) is less than 100 km² and its extent of occurrence (EOO) is 2,705 km², which meets the thresholds for Endangered under criteria B1 and B2.

The taxonomy of the Lucifuga genus is not yet complete, but is currently being researched. Although data are limited, the population size of L. lucayana is potentially very small. The characteristic low levels of oxygen within these caves is another significant limiting factor. Data on the life history of L. lucayana are limited. It has been inferred that Lucifuga species have a long generation length.

Threats to cave-dwelling species in the Caribbean include habitat degradation through rock removal or siltation, hydrological manipulations caused by water removal, environmental pollution, and the introduction of alien species. Typically, a cave that is near high densities of human populations is more threatened. Currently, Lucayan Caverns is protected within the Lucayan National Park, which is managed by the Bahamas National Trust and restricts recreational scuba diving to special permission only. The status of conservation in the Zodiac Caverns is unknown. A proposal for cave conservation of 17 blue holes on Great Abaco Island was submitted in 2010, but an updated status is not available. Further research on these restricted populations is needed. Lucifuga lucayana is assessed as Endangered (EN B1ab(iii)+B2ab(iii)).

Geographic Range [top]

Range Description:In general, Lucifuga spp. have highly patchy distributions, where they are only found in inland karst caves located near coastal margins (Garcia-Machado et al. 2011).

Lucifuga lucayana has been found in at least three inland cave or sink hole systems in the northern Bahamas to a depth of 20 m: the Lucayan Caverns in central southern Grand Bahama Island, the Zodiac Caverns on Sweetings Cay in eastern Grand Bahama, and one or two inland sink holes on Abaco Island (Little Bahama Bank). The range of this species is separated from that of L. spelaeotes by the deep waters of the Providence Channels. When L. spelaeotes was listed as Vulnerable on The IUCN Red List in 1996 (World Conservation Monitoring Centre 1996), its AOO was calculated as less than 100 km² with the number of recorded locations as less than five (Moller et al. 2006). This species is currently only known from three localities with an estimated EOO of 2,705 km² (based on a minimum convex polygon drawn around the extent of its range). Since not all caverns are mapped in the Bahamas, the AOO is currently unknown, however, it is inferred to be less than 100 km².
Countries occurrence:
Native:
Bahamas
FAO Marine Fishing Areas:
Native:
Atlantic – western central
Additional data:
Estimated area of occupancy (AOO) - km2:99
Lower depth limit (metres):20
Upper depth limit (metres):12
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Cave-diving expeditions can be logistically challenging and dangerous to undertake, therefore population data for L. lucayana are limited. The Lucifuga genus continues to evolve due to the discovery of new species in previously unexplored caves throughout the Caribbean. It will be difficult to grasp a complete understanding of the populations of Lucifuga spp. until a more detailed picture of their diversity and distribution is realized (Moller et al. 2006, Garcia-Machado et al. 2011). Garcia-Machado and Hernandez (2012) reported that populations of Lucifuga spp. tend to remain stable throughout the year.

This species was originally described from six specimens collected between the years 1980 and 1984 from two caves and one or two sink holes in the northern Bahamas. Due to very few specimens having been identified, the population size of L. lucayana may be small. Moller et al. (2006) calculated the population size of L. spelaeotes, a closely related species with a wider distribution but also endemic to the Bahamas, as less than 1,000 individuals.
Current Population Trend:Unknown
Additional data:
Population severely fragmented:Yes

Habitat and Ecology [top]

Habitat and Ecology:Lucifuga lucayana is a small, viviparous, eel-like fish with greatly reduced eyes that shies away from direct light where it lives in landlocked cave systems. It has been collected to a maximum size of 12.5 cm standard length (SL).

The environmental conditions of the sink holes are unknown, but both of the caves are anchialine in nature, where the top layer of water is fresh and the bottom is salty due to a subterranean connection to the sea. This species has been collected and observed from the fresh layer at Lucayan Caverns and from the salty layer at Zodiac Caverns, indicating that it is euryhaline in nature (Moller et al. 2006). Caribbean anchialine caves have very low levels of oxygen in the water and sediments, often with a boundary layer of hydrogen sulfide separating the fresh and salty (Hutchinson 1999, Bishop et al. 2004). The biogeochemistry of individual holes/caves vary widely, with particular sensitivity to solar insolation, water flow velocities, and organic matter inputs (Hutchinson 1999, Gonzalez et al. 2011). Due to the already harsh nature of this environment, even slight changes in cave water quality can negatively affect troglobitic organisms, which have already adapted with very low metabolic rates and small size so as to efficiently use energy when oxygen and food supply are lacking (Hutchinson 1999, Bishop et al. 2004, Gonzalez et al. 2011).

Food availability is a significant limiting factor for these cave fishes. Gonzalez et al. (2011) reported that food webs in these caves may be dependent on indigenous bacterial primary production. Populations of Lucifuga spp. seem to remain stable throughout the year, but the populations of the invertebrates that constitute their diet fluctuate significantly (Garcia-Machado and Hernandez 2012). The highest densities of Lucifuga spp. are usually observed hiding under ledges and in dark alcoves near the entrance where prey items tend to congregate (Trajano 2001). Lucifuga spp. are opportunistic, passive foragers that primarily prey on troglobitic amphipods and mysids, but will also eat crustaceans and shrimp (Trajano 2001, Moller et al. 2006, Garcia-Debras and Gonzalez 1999). Vegetable matter was found in the digestive tract of the holotype of L. simile. Populations of Lucifuga spp. are significantly more abundant in caves that bats also inhabit because their guano fertilizes the water and promotes growth of food sources for the fish (Garcia-Debras and Gonzalez 1999).

Data on the reproductive strategy of L. lucayana are limited, however, two other species of Lucifuga that are endemic to freshwater caves in Cuba have a breeding peak in March, with females carrying 2-15 embryos that are approximately 2.5 cm SL at birth (Eigenmann 1909). The ovaries in female fishes of the Lucifuga and Ogilbia genera are very similar, however, sexual structures of the male, though both intromittent, are different. Male fishes are characterized by the presence of an external reproductive organ anterior to the anal fin, which it uses to facilitate internal fertilization of females (Nielsen et al. 1999). It is thought that mating begins as soon as the female reaches maturity, when the female is able to carry and even nourish the delivered spermatozoa within their body for long periods of time. Throughout their five stages of development, the embryos of Ogilbia spp. obtain nutrients from yolk and ovigerous tissue produced within the female. Fecundity levels among bythitids vary greatly (Wourms 1981). The significantly smaller brood size of L. lucayana compared to other bythitid species, is probably due to a longer gestation of the embryos, which allow them to reach a more advanced stage of development, and consequently, allow for a greater chance of survival after birth (Suarez 1975). Reproduction may be infrequent and fecundity relatively low, but further research is needed (Trajano 2001, Garcia-Machado and Hernandez 2012). Definitive data on the longevity of L. lucayana are unknown, but it may be inferred that Lucifuga spp. have a long generation length because their populations are small and there have been very few captures of juveniles or pregnant females (Garcia-Machado and Hernandez 2012).
Systems:Freshwater; Marine
Continuing decline in area, extent and/or quality of habitat:Yes
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade:

Lucifuga lucayana is not utilized.

Threats [top]

Major Threat(s): Lucifuga lucayana may be experiencing direct threats from habitat degradation and introduced alien species. Proudlove (2001) described five main threats to cave-dwelling species: habitat degradation through rock removal or siltation, hydrological manipulations caused by water removal, environmental pollution, overexploitation, and the introduction of alien species. On multiple occasions, people have reported evidence of trash, sewage, industrial pollution, and competition from introduced species in caves throughout the range of all Caribbean Lucifuga spp. (Hutchinson 1999, Proudlove 2001, Proudlove 2006, Moller et al. 2006, Garcia-Machado et al. 2011). The level of impact and rate of occurrence of these disturbances directly correlates to the location of the cave/hole in relation to human population density. A hole/cave that is distantly located and difficult to access will remain more pristine and unaltered (Proudlove 2001). In contrast, increasing human population density around a subterranean habitat is a threat. There is concern that caves that are proximal to dense human populations could be exposed to insecticide spraying (Hutchinson 1999).

Scuba divers can be detrimental to these caves when they disturb the stratification of bacterial mats that lie near the halocline, enrich the levels of oxygen in the water, and perhaps introduce flora and fauna to the system. Some opinions, however, are that any information gained from further exploration of these environments may overcome the possible negative effects especially because a small proportion of these holes are likely to be affected by such activity (Hutchinson 1999, Proudlove 2001).

Conservation Actions [top]

Conservation Actions: Lucifuga species play an important ecological role in the balance of caves that they inhabit (Garcia-Debras and Gonzalez 1999). The threats of ongoing habitat degradation by human activities within the extremely limited distribution and the more recent widespread introduction of alien species that deplete the limited food supply of Lucifuga spp. require the attention of conservationists. Since species diversity for the Lucifuga genus is likely underestimated due to the incomplete exploration of their highly fragmented distribution, implementing conservation could be difficult without a more complete list of specific holes/caves that currently harbour populations (Garcia-Machado et al. 2011).

Some Lucifuga species have been successfully bred in captivity, which could prove beneficial if a population needs replenishment (Proudlove 2001). Lucifuga simile has been raised successfully on a diet of Troglocubanus spp. (cave shrimp) (Garcia-Debras and Gonzalez 1999). Further research on rearing L. lucayana should be explored.

The Lucayan Caves are contained within the Lucayan National Park, which is managed by the Bahamas National Trust, an organization tasked with the conservation of the country's natural resources. Diving in the Lucayan Caves is regulated to certain areas and is allowed only by special permission from the Underwater Explorers Society to experienced and trained divers. Details on diving in the Zodiac Caverns and holes on Abaco Island are not available at this time. The Bahamas Caves Research Foundation, drafted a proposal in the year 2010 that would protect 17 blue holes on Great Abaco Island and create awareness about cave conservation (Kakuk and Patterson 2010). Efforts to contact both the BNT and BCRF via email to request further information on conservation measures specific to these cave environments were largely unanswered. Proudlove (2001) reported that most Lucifuga species listed as threatened or more are not receiving necessary conservation attention. Habitat management, monitoring, education, and economic activities surrounding subterranean cave systems should be considered during the planning process (Garcia-Machado et al. 2011, Garcia-Machado and Hernandez 2012).

Citation: Dooley, J., Collette, B., Aiken, K.A., Marechal, J. & Pina Amargos, F. 2015. Lucifuga lucayana. The IUCN Red List of Threatened Species 2015: e.T16467724A16510047. . Downloaded on 25 May 2018.
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